The subject matter disclosed herein relates generally to diagnostic imaging and, more particularly, to an electrical inter-connect device for connection of electrical components within X-ray tubes and a method of manufacturing same.
Presently available medical X-ray tube designs typically include an insert assembly that houses a cathode assembly having an emitter or filament and a cathode cup and an anode assembly. The cathode assembly is oriented to face an X-ray tube anode assembly, or target, which is typically a planar metal or composite structure. The space within the X-ray tube between the cathode and anode is evacuated.
X-ray tubes typically include an electron source, such as a cathode, that releases electrons at high acceleration. Some of the released electrons may impact a anode target. The collision of the electrons with the anode target produces X-rays, which may be used in a variety of medical devices such as computed tomography (CT) imaging systems, X-ray scanners, and so forth.
To emit the electrons, the cathode assembly typically is operated at high voltage and includes a filament or electron emitter that requires current to be run through it to in order to produce the electrons as part of a process whereby the x-rays are generated after electrons hit the anode at a lower or zero high voltage potential. To supply current to the cathode assembly operated at high voltage, current X-ray tube designs also include a high voltage (hv) connector assembly that is typically attached mechanically and electrically to the cathode assembly.
The electrical connection between the cathode assembly and the hv connector assembly provides a path for conducting current between the hv connector and the cathode assembly, and directs that current along the path provided to the filament or emitter to generate electrons. As shown in FIG. 1A, the electrical connection utilized with prior art X-ray tube designs includes an inter-connect/connector pin 1000 on the hv connector that allows the transfer of current between the hv connector and cathode assembly. The pin 1000 includes an outer housing or cylinder 1002 engaged with the hv connector and an inner housing or cylinder 1004 disposed co-axially within the outer cylinder 1002. The inner cylinder 1004 houses a spring 1006 that is compressed between an end of the inner cylinder 1004 and a ball 1008. The ball 1008 is pressed by the spring 1006 against a plunger 1010 that is slidably mounted within the inner cylinder 1004. The plunger 1010 terminates in an engagement structure or hat 1012 that is pressed against a contact terminal (not shown) located on an hv insulator of the cathode assembly in order to create the electrical connection and current path between the hv connector and the cathode assembly.
The plunger 1010 is formed with a head 1014 located adjacent the ball 1008. The head 1014 includes a sloped surface 1016 that engages the ball 1008. The orientation of the sloped surface 1016 allows the force exerted by the spring 1006 on the head 1014 through the ball 1008 to urge the plunger 1010 axially out of the inner cylinder 1004 and radially into contact with the inner cylinder 1004. By urging the head 1014 of the plunger 1010 into contact with the inner cylinder 1004, when the current is directed through the pin 1000 to the cathode assembly, the path taken by the current goes from the outer cylinder 1002 to the inner cylinder 1004 at a point near the head 1014, then from the inner cylinder 1004 to the plunger 1010 via the head 1014, and finally from along the plunger 1010 to the hat 1012 for transmission to the contact point on the cathode assembly.
In these prior art hv connectors, to avoid the use of a blind, tight-tolerance connection between a socket or bore (not shown) in the cathode assembly and the pin 1000, which could easily result in damage to the pin 10, the construction of the pin 1000 is designed to allow the hv connector to “float” with respect to the cathode assembly. Thus, the hat 1012 is not engaged within a bore but is pressed against a contact point on the surface of the cathode assembly within a tolerance of 1-2 mm that still provides the necessary electrical connection between the hv connector and the cathode assembly.
However, as a result of slight forces exerted on the hat 1012 and plunger 1010 during installation and/or use of the imaging device including the hv connector, the plunger 1010 can be shifted radially within the inner cylinder 1004. This shift moves the head 1014 out of contact with the inner cylinder 1004 and creates a different current path through the pin 1000. As shown in FIG. 1B, in this situation the current flows from the outer cylinder 1002 to the inner cylinder 1004, from the inner cylinder 1004 through the spring 1006, from the spring 1006 to the ball 1008, and finally from the ball 1008 to the head 1014 of the plunger 1010. This alternative current path results in significant heating of the spring 1006, which consequently anneals the spring 1006 and causes it to lose its biasing capability. As a result, with no spring bias or force to create contact between the ball 1008 and the plunger 1010, and consequently between the hat 1012 and the contact point on the hv insulator, the X-ray tube is rendered incapable of generating X-rays, such that the hv connector and/or the defective pin 1000 must be removed and replaced, resulting is significant downtime for the imaging device.
Hence it is desirable to provide a hv connector including a pin construction that can significantly reduce the transmission of current through pin along the main failure current path through the spring, thereby increasing the useful life of the hv connector, reducing down-time at hospitals due to failed X-ray tubes and the need for X-ray tube replacement.